Stationary Thermal Conditions Research Articles

Thermal efficiency of the enclosing structures of an individual residential house in conditions of interconstant thermal energy generation

The involvement of recycled wood resources and low-quality wood in the processing provides an active source of raw materials for the construction industry. Environmentally friendly building materials in the form of wood-mineral composites (WMC) help recycle this waste and help conserve natural resources. The study examined the thermal performance of enclosing structures in the form of a frame wall filled with mineral wool, walls made of aerated concrete blocks and stands made of WMC. The purpose of the work was to determine the thermal regime of enclosing structures under stationary and non-stationary thermal conditions. The unsteady mode was created by simulating the generation of thermal energy for 10 hours a day. The mode corresponds as closely as possible to the actual operating conditions of an individual housing construction project, provided that it is heated by a solid fuel boiler or stove with periodic generation of thermal energy. The total simulation time is 5 days. It has been established that in a stationary thermal mode, all considered structures comply with sanitary and hygienic requirements and heat conservation standards.

Synthesis and Properties of Silicon Carbide (Review)

Silicon carbide is an extremely hard material that exhibits exceptional corrosion resistance as well as thermal shock resistance. Its high mechanical properties determine the increased performance of materials based on it. The combination of high thermal conductivity and low thermal expansion coefficient determines the stability of silicon carbide at high heating rates and under stationary thermal conditions. To date, significant progress has been made in the development of methods for the synthesis of various materials based on silicon carbide. The main synthesis methods that scientists use in their research are the sol-gel method, sintering, pyrolysis, microwave synthesis, chemical vapor deposition, etc. The use of "green" techniques in the synthesis of SiC has gained wide popularity due to environmental friendliness, renewability, and ease of implementation. This review analyzes modern research in the field of silicon carbide synthesis published in peer-reviewed professional journals.

A model of shapes of liquid cylindrical inclusions migrating through a non-uniformly heated crystal: Fundamentals and applications for studying crystallization and dissolution

A model of shapes of liquid cylindrical inclusions migrating through a non-uniformly heated crystal: Fundamentals and applications for studying crystallization and dissolution

Thermal conductivity of geopolymer concrete with different types of aggregate

In this article the influence of aggregate of geopolymer concrete used in concrete printing of buildings and structures, architectural elements on its thermal conductivity is studied. All tests were conducted on device for measuring thermal conductivity called PIT-2 designed to measure the thermal conductivity of building and heat-insulating materials under stationary thermal conditions in accordance with ISO 7345:1987* and ISO 9251:1987. As the fine aggregate most commonly used river sand, quartz sand, ceramic foam, as well as one new coniferous shavings were taken. The results of 4 tests to determine the thermal conductivity of geopolymer concrete with various aggregates are listed in the summary table in the study. According to the test results, the lowest coefficient of thermal conductivity has geopolymer concrete on ceramic foam. In this study geopolymer concrete is considered as the main material for concrete printing of the houses and architectural forms. This material reduces CO2 emissions in the atmosphere.

Influence of thermal insulation of the wall area of the floor on the ground on the heat loss amount

The relevance of the study is explained by the fact that in the Russian Federation, the “by zone” method of heat loss calculations of the floor on the ground does not allow considering various factors that affect heat losses. As the heat loss studying method, this work adopts the calculation of the non-stationary annual thermal regime of floors together with the soil mass. There is no such thermal protection indicator as the heat transfer resistance in a non-stationary thermal process, therefore the paper uses a characteristic, in other words, a conditionally reduced one for heat loss calculations through the floor on the ground in stationary thermal conditions. The purpose of this article is to calculate the average characteristic heat transfer resistances for each design zone for thermal protection of the wall area of the floor on the ground with different width of the insulation stripe and heat transfer insulation resistance. The considerable result of the work is detection of significant impact of the soil type, the width of the floor insulation stripe, and the actual resistance to heat transfer of this insulation on the characteristic heat transfer resistance in the first design zone. It follows from the study that the floor thermal insulation stripe in the wall area is the most effective structure of the floor thermal protection, both in terms of reducing heat losses, and in terms of compliance with the temperature standards for the floor.

A DEVICE FOR STUDYING THE THERMOPHYSICAL PROPERTIES OF BULK TEXTILE MATERIALS AND THEIR PACKAGES BY THE REGULAR MODE METHOD IN AIR

Textile fabrics have different heat transfer properties, which depend on the conditions of consumption of the product and various types of processing. All this is of scientific interest for identifying factors and features of individual materials. The purpose of the study was to track heat transfer through packages of multilayer textile materials in stationary and transient thermal conditions. A particular property of textile materials lies in their ability to deform under their weight so that a sample can be placed between meshes of a material with high heat resistance. Heat transfer is carried out by convective heat transfer between the surface of the material and the air. To conduct this study, the Fourier law was used in the calculations and numerical methods for solving heat conduction problems. The developed program, which was created for the study, permit to write parameters to a computer and uses them to calculate the thermophysical properties of the sample. As a result of the work, graphs of the state of the package of materials were presented, and a device was proposed that allows to determine the modes that characterize the thermophysical properties of the materials used in the manufacture of clothing and its packages. The device admits with high accuracy to record, record and store changes in the parameters at which studies were conducted.

PORTABLE HEAT METERING SYSTEM DESIGN

In modern construction practice, more than half of buildings in operation require modernization of thermal insulation. However, in order to select an effective insulation system, it is necessary to know the actual thermal and technical characteristics of structures and parameters of the building internal environment. The paper analyzes methods and equipment for evaluation of the thermal performance of outdoor enclosures. The advantages and disadvantages of the main devices recommended by the regulatory documents for field research are shown. According to the data obtained, a heat engineering complex is developed for conducting field studies of heat and humidity of wall structures and microclimate of building premises. Software improvement together with Arduino reader device allow monitoring both at stationary and non-stationary thermal conditions of external enclosures and indoor climate parameters in field conditions.

Экспериментально-расчетная методика оценки теплофизических характеристик строительных материалов с использованием камерной электропечи для решения задач огнестойкости

Цель. На основе экспериментальных исследований и теоретических данных разработать методику и определить теплофизические характеристики цементно-армированных и минераловатных плит при повышенных температурах для решения задач огнестойкости.
 Методы. Использованы методы конечных элементов, параметрической оптимизации, экспериментальные исследования.
 Результаты. Разработана методика и проведены экспериментальные исследования по прогреву исследуемых материалов в рамках границ температурно-временной кривой стандартного пожара: в стационарном тепловом режиме при температурах 275, 550, 770 и 1150 °С; в нестационарном тепловом режиме при температурах от 20 до 1000 °С. Разработаны расчетные конечно-элементные модели, сформулированы краевые (начальные и граничные) условия, с использованием методов параметрической оптимизации определены теплофизические характеристики цементно-армированных и минераловатных плит при повышенных температурах для решения задач огнестойкости.
 Область применения исследований. Полученные результаты могут быть использованы для решения задач огнестойкости строительных конструкций на основе минеральных утеплителей и цементно-армированных плит, а также для определения теплофизических характеристик при повышенных температурах иных строительных материалов.

Analysis of the main parameters of crude oil pipeline transport

The paper presents results of experimental research and simulation of the main parameters of crude oil pipeline transport. In Serbia, 70 % of the produced oil belongs to a paraffin type, of which over 25 % has a high content of paraffin. High-content paraffin oil usually has a high pour point. The paraffin content in crude oil from Vojvodina, Serbia, is in the range 7.5 to 26 %, and the oil pour temperature varies from 18 to 36?C. The imported crude oil has a flow point max. 8?C. Homogenization, i.e. mixing of domestic and imported crude oil, improves the transport properties and decreases the pour point. After homogenization, the crude oil is pre-heated, and then transported by a pipeline to the refinery for further processing. Heating induces modification of crude oil physical properties, especially flow properties so to prevent wax formation within the oil pipeline. The aim of this paper was to determine operating parameters and flow characteristics for a particular oil pipeline (428 mm inner diameter, 91,000 m length) under real operating conditions. By heating in the range of 20 - 50?C, the viscosity of crude oil was reduced, approaching the viscosity of water. The pipeline is isolated (100 mm thick isolation) and buried into in the ground (1 m depth). It is found that the heat transfer coefficient has a dominant influence on the cooling rate of the oil in the pipeline. The heat transfer coefficient is mainly determined by the isolation thickness so that it was determined as 0.60 W m-2 K-1 for + 100 mm thickness, while it was 2.20 W m-2 K-1 for the non-isolated pipeline. Heat losses through the main pipeline ranged from 36 - 110 kJ m-1 h-1 (10 - 30 W m-1). The difference between the starting and the ending temperature of crude oil ranged from 10 to 12?C. Such a decrease of ?t = 10 oC and, consequently, the increase in viscosity induced a noti-ceable increase in the pressure drop and pump power by 3 to 4 %, at the maximum flowrate of 0.194 m3 s-1 (700 m3 h-1). The cooling rate during transportation under stationary thermal and hydraulic conditions is in the range 0.52 ? 0.5 oC h-1. In the case of domestic oil (Vojvodina, Serbia) transport, the downtime should not exceed 24 h, since stopping and cooling of the oil would result in formation of solid paraffin particles followed by oil gelation.

On Thermomigration Velocity of Liquid Cylindrical Inclusions in a Crystal under Stationary Thermal Conditions

The dependences of the velocity and the cross section shape of the inclusion on the cross sectional area at the various interfacial energy density, degree of its anisotropy, and degree of difficulty of the interfacial processes have been calculated and analyzed on the basis of model ideas on the cross section shape of the liquid cylindrical inclusion migrating in a crystal under the action of a temperature gradient in stationary thermal conditions. The possibility of the nonmonotonic dependence of the velocity of the cylindrical inclusion on the area and thickness of its cross section is shown.

О скорости термомиграции жидких цилиндрических включений в кристалле в стационарных тепловых условиях

Based on model ideas about the cross-sectional shape of a liquid cylindrical inclusion migrating through a crystal under the action of a temperature gradient in the case of the stationary thermal conditions, the dependences of the velocity and cross-sectional shape of the inclusion on its cross-sectional area have been calculated and analyzed for different values of the specific interfacial energy, the degree of its anisotropy, and the degree of difficulty of interface processes. The possibility of a nonmonotonic dependence of the velocity of the cylindrical inclusion on the area and thickness of its cross section has been shown.

On a Technique of Studying the Interface Kinetics and Anisotropy of Specific Interfacial Energy Based on Experiments on Migration of Liquid Cylindrical Inclusions in a Crystal under Stationary Thermal Conditions

A method for processing experimental data on the migration of liquid cylindrical inclusions in a crystal under a temperature gradient has been considered on the assumption that the experimental thermal conditions are stationary. Formulas are derived to calculate the degree of interfacial energy anisotropy and relative hindrance of the crystallization and dissolution processes at atomically smooth interface areas based on the shapes of cross sections of cylindrical inclusions migrated perpendicular to the close-packed crystal planes.

Fibre Bragg Gratings to monitor the deformations of a silicon microstrip vertex detector

Fibre Bragg Gratings to monitor the deformations of a silicon microstrip vertex detector

Investigation of heating of 150 kV underground cable line for various conditions of laying

The work is devoted to study of temperature operation of a 150 kV underground cable line with XLPE insulation. The stationary thermal conditions were calculated. The influence of outer boundary radius selection on the temperature distribution was analyzed.The limiting value of the filling mixture thermal conductivity was found, which provides an acceptable temperature of the cable.

Russian

Russian

Modeling the stationary thermal conditions of a premises heated by a passive insolation system containing a three-layer translucent shield with a partially ray-absorbing film on its inner surface

The results from modeling the stationary thermal conditions of a premises equipped with a passive insolation heating system containing a three-layer translucent shield (TLS) are presented to derive analytical equations for calculating the average daily air temperature inside the premises, and the thermal load displacement factor of the considered system.

Evaluation of Wall Paint Emissivity During Infrared Thermography Temperature Measurement

In cases that the temperature of large surfaces needs to be measured, because measuring by conventional temperature equipment is time consuming, thermography is a fast and simple alternative solution. The most important feature that affects the amount of energy radiating from a surface, under stationary thermal conditions (fixed temperature), is its emissivity. In the present study emissivity of certain commercial wall paints was determined experimentally by adjusting its value in an infrared thermal imager, until its readings coincided with a known temperature measured by PT-100 sensors. It was shown that the emissivity is dependent on the color, current temperature and type/texture of the material.

STATIONARY THERMAL BEHAVIOR ANALYSIS OF CURRENTCARRYING SYSTEMS OF POWER ELECTRIC AND ELECTRONIC EQUIPMENT

Computation method of stationary thermal conditions determination of power electric and electronic equipment of current-carrying systems is proposed. The method differs in considerable versatility and takes into account a great number of various components with distinctive conditions of heat release and heat transfer in complex current-carrying system.

Evaluation of Wall Paint Emissivity during Infrared Thermography Temperature Measurement

In cases that the temperature of large surfaces needs to be measured, because measuring by conventional temperature equipment is time consuming, thermography is a fast and simple alternative solution. The most important feature that affects the amount of energy radiating from a surface, under stationary thermal conditions (fixed temperature), is its emissivity. In the present study emissivity of certain commercial wall paints was determined experimentally by adjusting its value in an infrared thermal imager, until its readings coincided with a known temperature measured by PT-100 sensors. It was shown that the emissivity is dependent on the color, current temperature and type/texture of the material.

Evaluation of Wall Paint Emissivity during Infrared Thermography Temperature Measurement

In cases that the temperature of large surfaces needs to be measured, because measuring by conventional temperature equipment is time consuming, thermography is a fast and simple alternative solution. The most important feature that affects the amount of energy radiating from a surface, under stationary thermal conditions (fixed temperature), is its emissivity. In the present study emissivity of certain commercial wall paints was determined experimentally by adjusting its value in an infrared thermal imager, until its readings coincided with a known temperature measured by PT-100 sensors. It was shown that the emissivity is dependent on the color, current temperature and type/texture of the material.